Servo Control Apparatus Sensorless Stop Observer
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Solution Overview
Problem
Conventional servo control systems cannot perform a controlled stop in the event of a sensor malfunction, leading to excessive stopping distances and potential machine damage due to collisions, especially in high-inertia or high-speed motor operations.
Innovation Solution
A servo control apparatus that switches to a sensorless control method by using voltage information to estimate motor speed and generate a stop position or deceleration command, incorporating a sensor malfunction detector and switches to transition from actual to estimated sensor feedback, enabling a controlled stop even without functional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dynamic brake resistor is used to stop the motor during sensor malfunction, then the motor can be stopped, but the stopping distance becomes excessive leading to potential machine damage
Solution Approach 1:
The patent replaces the purely mechanical/passive dynamic brake stopping method with an active control system that uses estimated sensor information (via observer) to generate controlled stop commands. This substitutes the inadequate mechanical brake-only approach with a sophisticated control algorithm that can actively manage the motor deceleration profile even without actual sensor feedback, thereby reducing stopping distance while maintaining safety.
Solution Approach 2:
The patent introduces an observer (state estimator) as an intermediary that generates estimated sensor information (position, speed, magnetic pole position) when actual sensors fail. This estimated information acts as a mediator between the control system and the motor, enabling the controlled stop function to operate continuously even during sensor malfunction, thus preventing excessive stopping distances.
2Length of moving object
If conventional controlled stop methods are used, then the stopping distance is shortened, but they cannot be used during sensor malfunction because sensor information is required
Solution Approach 1:
The observer serves as an intermediary that provides estimated sensor information to the controlled stop algorithm when actual sensors are malfunctioning. This allows the controlled stop method to maintain its short stopping distance capability while becoming adaptable to sensor failure conditions, resolving the contradiction between stopping distance performance and operational versatility.
Solution Approach 2:
The patent changes the source of sensor information parameters from actual physical sensors to estimated values generated by the observer algorithm. This parameter substitution enables the controlled stop function to operate during sensor malfunctions while maintaining accurate position, speed, and magnetic pole position information necessary for effective controlled stopping.
3Reliability
If sensor information is continuously monitored for malfunction detection, then sensor failures can be detected, but the system lacks the capability to perform controlled stop without actual sensor feedback
Solution Approach 1:
The observer acts as an intermediary that bridges the gap between sensor malfunction detection and controlled stop capability. When sensor failures are detected, the observer generates estimated information that enables the controlled stop function to continue operating, thus maintaining ease of operation even during sensor failures while preserving reliable malfunction detection.
Solution Approach 2:
The system prepares for sensor failures by having the observer continuously ready to provide estimated sensor information. This beforehand preparation ensures that when sensor malfunctions occur, the controlled stop capability is immediately available without interruption, cushioning against the potential loss of operational capability during sensor failures.
Data Source
AI summary
A servo control apparatus includes a sensor unit for detecting a motor speed; an amplifier for driving a motor and feeding back a current; a magnetic pole position detector; a position controller for outputting a speed command; a speed controller for outputting a current command; a current controller for outputting a voltage command; a speed estimator for calculating an estimated speed from the voltage command; a magnetic pole position estimator for calculating an estimated magnetic pole position from the estimated speed; a sensor malfunction detector; a stop position command generator; and a first switch for switching from the position command to the stop position command, a second switch for switching from the magnetic pole position to the estimated magnetic pole position, and a third switch for switching from the detected speed to the estimated speed, when the sensor malfunction detector has detected a malfunction.